rank_imagerank_imageRankImageRankImagerank_image (算子)

名称

rank_imagerank_imageRankImageRankImagerank_image — 使用任意掩模计算秩滤波。

签名

描述

rank_imagerank_imageRankImageRankImageRankImagerank_image performs a rank filter on the input image ImageImageImageImageimageimage with a mask that is specified by the region MaskMaskMaskMaskmaskmask and returns the filtered image in ImageRankImageRankImageRankImageRankimageRankimage_rank. The shape of the mask can be chosen arbitrarily and can, for example, be created with operators like gen_circlegen_circleGenCircleGenCircleGenCirclegen_circle or draw_regiondraw_regionDrawRegionDrawRegionDrawRegiondraw_region。The position of the mask does not influence the result since the center of gravity of the mask region is used as the reference point of the mask.

Conceptually, the rank filter sorts all gray values within the mask in ascending order and then selects the gray value with rank RankRankRankRankrankrank. The rank 1 corresponds to the smallest gray value and the rank A corresponds to the largest gray value within the mask. Here, A denotes the area of MaskMaskMaskMaskmaskmask (see area_centerarea_centerAreaCenterAreaCenterAreaCenterarea_center). For RankRankRankRankrankrank = (A - 1) / 2 + 1, rank_imagerank_imageRankImageRankImageRankImagerank_image returns the median gray value (see median_imagemedian_imageMedianImageMedianImageMedianImagemedian_image). For RankRankRankRankrankrank = 1, rank_imagerank_imageRankImageRankImageRankImagerank_image performs a gray value erosion (see gray_erosion_rectgray_erosion_rectGrayErosionRectGrayErosionRectGrayErosionRectgray_erosion_rect, gray_erosion_shapegray_erosion_shapeGrayErosionShapeGrayErosionShapeGrayErosionShapegray_erosion_shape, and gray_erosiongray_erosionGrayErosionGrayErosionGrayErosiongray_erosion), while for RankRankRankRankrankrank = A rank_imagerank_imageRankImageRankImageRankImagerank_image performs a gray value dilation (see gray_dilation_rectgray_dilation_rectGrayDilationRectGrayDilationRectGrayDilationRectgray_dilation_rect, gray_dilation_shapegray_dilation_shapeGrayDilationShapeGrayDilationShapeGrayDilationShapegray_dilation_shape, and gray_dilationgray_dilationGrayDilationGrayDilationGrayDilationgray_dilation).

rank_imagerank_imageRankImageRankImageRankImagerank_image can be used, for example, to suppress noise or to suppress unwanted objects that are smaller than the mask. Furthermore, rank_imagerank_imageRankImageRankImageRankImagerank_image is less sensitive to noise than the corresponding gray value morphology operators. Therefore, to obtain a more robust version of the gray value morphology, instead of using 1 or A, slightly larger or smaller values should be selected for RankRankRankRankrankrank。

Several border treatments can be chosen for filtering via the parameter MarginMarginMarginMarginmarginmargin: gray value Pixels outside of the image borders are assumed to be constant (with the specified gray value). 'continued' Continuation of border pixels. 'cyclic' Cyclic continuation of image borders. 'mirrored' Reflection of pixels at the image borders.

有关平滑滤波器概念的说明，请参阅 滤波器 / 平滑 一章的引言。

注意

rank_imagerank_imageRankImageRankImageRankImagerank_image uses an algorithm with a runtime per pixel that depends on the number of runs in the mask MaskMaskMaskMaskmaskmask. Therefore, rank_imagerank_imageRankImageRankImageRankImagerank_image is slower than rank_rectrank_rectRankRectRankRectRankRectrank_rect for rectangular masks with a large mask height. The precise mask height for which rank_rectrank_rectRankRectRankRectRankRectrank_rect will become faster than rank_imagerank_imageRankImageRankImageRankImagerank_image depends on the computer architecture (processor type, availability of SIMD instructions like SSE2 or MMX, cache size and throughput, memory throughput). Typically, this is the case for mask heights > 15, but can also be the case only for larger mask sizes, e.g., if SIMD instructions are unavailable and memory throughput is low.

Furthermore, it should be noted that rank_rectrank_rectRankRectRankRectRankRectrank_rect uses a recursive implementation, which internally computes the filter response on the smallest enclosing rectangle of the domain of the input image. Therefore, if the domain of the input image only covers a small fraction of the smallest enclosing rectangle, it can happen that rank_imagerank_imageRankImageRankImageRankImagerank_image is faster than rank_rectrank_rectRankRectRankRectRankRectrank_rect even for larger mask heights.

rank_imagerank_imageRankImageRankImageRankImagerank_image should neither be used with RankRankRankRankrankrank = 1 to perform a gray value erosion nor with RankRankRankRankrankrank = A to perform a gray value dilation. In these cases, the operators gray_erosion_rectgray_erosion_rectGrayErosionRectGrayErosionRectGrayErosionRectgray_erosion_rect, gray_erosion_shapegray_erosion_shapeGrayErosionShapeGrayErosionShapeGrayErosionShapegray_erosion_shape, or gray_erosiongray_erosionGrayErosionGrayErosionGrayErosiongray_erosion and gray_dilation_rectgray_dilation_rectGrayDilationRectGrayDilationRectGrayDilationRectgray_dilation_rect, gray_dilation_shapegray_dilation_shapeGrayDilationShapeGrayDilationShapeGrayDilationShapegray_dilation_shape, or gray_dilationgray_dilationGrayDilationGrayDilationGrayDilationgray_dilation, respectively, are typically faster than rank_imagerank_imageRankImageRankImageRankImagerank_image.

请注意，若使用域缩减后的图像作为输入，滤波器算子可能会返回意外结果。请参阅 滤波器 一章

执行信息

• 多线程类型：可重入（与非独占算子并行运行）。
• 多线程作用域：全局（可从任何线程调用）。
• 在元组级别上自动并行化。
• 在通道级别上自动并行化。
• 在域级别上自动并行化。

参数

示例（HDevelop）

read_image (Image, 'fabrik')
draw_region (Region, WindowHandle)
rank_image (Image, Region, ImageRank, 5, 'mirrored')
dev_display(ImageRank)

复杂度

For each pixel: O(N), where N is the number of runs of MaskMaskMaskMaskmaskmask (see runlength_featuresrunlength_featuresRunlengthFeaturesRunlengthFeaturesRunlengthFeaturesrunlength_features).

结果

如果参数值正确，算子 rank_imagerank_imageRankImageRankImageRankImagerank_image 返回值 2 ( H_MSG_TRUE )。当输入为空（无可用输入图像）时可设置行为通过算子 set_system('no_object_result',<Result>)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)set_system("no_object_result",<Result>)。如有必要，则抛出异常。

可能的前趋

read_imageread_imageReadImageReadImageReadImageread_image, draw_regiondraw_regionDrawRegionDrawRegionDrawRegiondraw_region, gen_circlegen_circleGenCircleGenCircleGenCirclegen_circle, gen_rectangle1gen_rectangle1GenRectangle1GenRectangle1GenRectangle1gen_rectangle1, gen_rectangle2gen_rectangle2GenRectangle2GenRectangle2GenRectangle2gen_rectangle2

可能的后继

thresholdthresholdThresholdThresholdThresholdthreshold, dyn_thresholddyn_thresholdDynThresholdDynThresholdDynThresholddyn_threshold, regiongrowingregiongrowingRegiongrowingRegiongrowingRegiongrowingregiongrowing

替代

rank_rectrank_rectRankRectRankRectRankRectrank_rect, median_imagemedian_imageMedianImageMedianImageMedianImagemedian_image, median_rectmedian_rectMedianRectMedianRectMedianRectmedian_rect

另见

gray_erosion_rectgray_erosion_rectGrayErosionRectGrayErosionRectGrayErosionRectgray_erosion_rect, gray_dilation_rectgray_dilation_rectGrayDilationRectGrayDilationRectGrayDilationRectgray_dilation_rect, gray_erosion_shapegray_erosion_shapeGrayErosionShapeGrayErosionShapeGrayErosionShapegray_erosion_shape, gray_dilation_shapegray_dilation_shapeGrayDilationShapeGrayDilationShapeGrayDilationShapegray_dilation_shape, gray_erosiongray_erosionGrayErosionGrayErosionGrayErosiongray_erosion, gray_dilationgray_dilationGrayDilationGrayDilationGrayDilationgray_dilation

参考文献

T.S. Huang, G.J. Yang, G.Y. Tang; “A Fast Two-Dimensional Median Filtering Algorithm”; IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. 27, no. 1, pp. 13-18, 1979.
R. Haralick, L. Shapiro; “Computer and Robot Vision”; Addison-Wesley, 1992, pp. 318-320.

模块

基础

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